IC-NZN_12 Datasheet, PDF (9/17 Pages) IC-Haus GmbH – N-TYPE LASER DIODE DRIVER

iC-NZN
N-TYPE LASER DIODE DRIVER
preliminary
Rev B2, Page 9/17
RMON = ^{V (MD)} = ^{0.5 V} = 33.34 kΩ
IM
15 µA
External capacitor mode
In applications where an external capacitor is required
(see best performance recommendations below), the
external capacitor mode must be enabled (pin CID =
high). This connects the capacitor to the control cir-
cuit and additionally enables a pull-down current at pin
CI to prevent this capacitor from being charged due
to residual currents (cf. Electrical Characteristics No.
406).
lead to an unstable control circuit under certain condi-
tions such as inadequate PCB layout or laser diodes
with very low monitor current. In these cases, an op-
tional capacitor can be connected as close as possible
to the chip, across pin CI and CIS. This will prevent
instability of the control circuit. For averaging control
a 10 nF capacitor at CI is recommended. Special care
must be taken in PCB layout when laying out the path
from the laser diode’s cathode via pin LDK to AGND.
This path must be kept as short as possible to avoid
parasitic inductances. A sbubber network across the
laser diode helps to compensate for these parasitic in-
ductances.
Best performance recommendations
The operating point for the laser diode is stored in an
on-chip capacitor. This permits a fast start-up but can
Figures 3, 4 and 5 show the typical set-up for the dif-
ferent N, P and M-type diode configurations.
N-type diodes
+3..+5.5V
CVDD
100 nF..
RSI
0.68.. 9kΩ
GND
VDD
RSI
NSLP
REGE
i(RSI)x540
LDA MONITOR
VD D
AVG
&
VSY
SYN
EP
EN
TTL
LVDS/TTL
+
-
VD D
CID
NERR
T.PAD
GND
INPUT INTERFACE
OverTemp.
1
OverCurrent
Low V(LDA)
RVDD
LDA
iC-NZN
IMON
&
1
LDK
+
REF
-
x240
CI
CIS
ECI
AGND
MD
ECI
OUTPUT DRIVER
Bandgap, Reference, Overtemp
OUTPUT MONITOR
RGND
N
..300mA
CI
..10 nF..
RMD
PMD
CLDA
100 nF..
Figure 3: Circuit example for N-type laser diodes
P-type diodes
Althought this kind of laser diodes are supported by iC-
NZN, it’s strongly recommended to use iC-NZP instead
since in this configuration, all the pulses at LDK will
be coupled directly to pin MD due to monitor diode’s
internal capacitance, thus making an accurate control
much more difficult. Moreover, applications with P-type
laser diode case grounded are possible with iC-NZP
only.